The increasing use of Web services as well as the growing interest lent to Cloud computing technology and its capacity of calculation, storage and Cloud services, impose today that the traditional mechanisms of discovery and selection must be re-examined. This specificity of discovery over the cloud led us to propose a new framework based on mobile agents dedicated to Web services discovery and selection. More accurately, we propose a new algorithm of comparison between the request of the client and the description of the Web services. Our system is composed of two regions of Cloud. The first deals with the discovery of web services based on Key words and the second supports the selection of the found web services based on WordNet lexical database. This discovery is performed by an algorithm based on the calculation of similarities between the request and the descriptions of the web services. The results show that our system: enhance the quality of our Cloud service (response time and Global cost), due to our virtualization policy, and benefit from the characteristics of the Open Cloud Computing Federation concepts, using Mobile agents to relate the different Cloud computing regions.